Best method to gradually change light settings while holding a button?

I have a light attached to the player that I want them to be able to "focus" when holding a button. Think Alan Wake (but in first person). Right now I have the following settings:

Spotlight "Focused" Settings While Holding Button:

• Outer Cone = 30
• Inner Cone = 20
• Intensity = 12000

Spotlight Default Settings When Button Released:

• Outer Cone = 65
• Inner Cone = 30
• Intensity = 3000

However, this instant change doesn't feel great, so I wanted to make the change gradual, so it feels more like the beam is "powering up". I tried using Timelines for each setting, and then using the Reverse of the Timelines when the button is released, but it is acting odd. The very first time I press the button, there is a gradual change in the light settings, but every subsequent time it seems to revert back to being an instant change.

Is there something other than Timelines I can use to create such an effect?